A power supply board in a liquid crystal display apparatus (for example, a liquid crystal display and a liquid crystal display television) is configured to convert an inputted alternating current into a direct current to provide power supply for a backlight source and a liquid crystal driving circuit and so on. If there occurs in the backlight source and the liquid crystal driving circuit which are load of the power supply board a short circuit, it may result in over current, which would cause occurrence of hazardous conditions such as wire stock on fire and so on.
There already exists a corresponding protection circuit in the current power supply board to protect the condition of short circuit occurring to the load of the power supply board. An output voltage is monitored by the way of voltage dividing of resistors. When abnormality occurs to the voltage (for example, the output voltage is excessive), the power supply output is cut off to protect the load. However, when the load is shorted circuit, the current in the power supply board rises suddenly within a short time, which would cause strong current attack on devices of the load and the power supply board, and may cause damage to part of devices before the power supply output is cut off.